Norasikin Ahmad Ludin

A review of organic small molecule-based hole-transporting materials for meso-structured organic-inorganic perovskite solar cells

This review summarizes the current designs and development of new types of organic small molecules as a hole-transporting material (HTM) in a meso-structured perovskite solar cell (PSC). The roles of each layer in the meso-structured perovskite device architecture are elaborated and the employment of new types of organic HTMs in the device is compared with the commercially available HTM spiro-OMeTAD in terms of the properties, device performance and stability. The studies found that nearly half of the new synthesized and pristine HTMs have comparable or better photovoltaic properties than those of doped spiro-OMeTAD. These HTMs have the characteristics of a fused planar core structure with extended π-conjugated lengths and electron-donating functional groups, which are believed to contribute to their high intrinsic conductivity and help make them an alternative to spiro-OMeTAD as a better HTM in meso-structured PSCs. Some of the devices based on the new synthesized HTMs even have longer device lifetimes than their spiro-OMeTAD-based PSC counterparts. Moreover, studies found that the cost per gram (Cg) and cost-per-peak Watt (Cw) of synthesized HTMs can be reduced via minimizing the number of synthesis steps and by optimization of the starting materials in order to yield low-cost HTMs for meso-structured PSC applications.

Carbonaceous materials and their advances as a counter electrode in dye-sensitized solar cells: Challenges and prospects

Dye-sensitized solar cells (DSSCs) serve as low-costing alternatives to silicon solar cells because of their low material and fabrication costs. Usually, they utilize Pt as the counter electrode (CE) to catalyze the iodine redox couple and to complete the electric circuit. Given that Pt is a rare and expensive metal, various carbon materials have been intensively investigated because of their low costs, high surface areas, excellent electrochemical stabilities, reasonable electrochemical activities, and high corrosion resistances. In this feature article, we provide an overview of recent studies on the electrochemical properties and photovoltaic performances of carbon-based CEs (e.g., activated carbon, nanosized carbon, carbon black, graphene, graphite, carbon nanotubes, and composite carbon). We focus on scientific challenges associated with each material and highlight recent advances achieved in overcoming these obstacles. Finally, we discuss possible future directions for this field of research aimed at obtaining highly efficient DSSCs.

Effect of solvents on the extraction of natural pigments and adsorption onto TiO2 for dye-sensitized solar cell applications

Nine solvents, namely, n-hexane, ethanol, acetonitrile, chloroform, ethyl-ether, ethyl-acetate, petroleum ether, n-butyl alcohol, and methanol were used to extract natural dyes from Cordyline fruticosa, Pandannus amaryllifolius and Hylocereus polyrhizus. To improve the adsorption of dyes onto the TiO2 particles, betalain and chlorophyll dyes were mixed with methanol or ethanol and water at various ratios. The adsorption of the dyes mixed with titanium dioxide (TiO2) was also observed. The highest adsorption of the C.fruticosa dye mixed with TiO2 was achieved at ratio 3:1 of methanol: water. The highest adsorption of P.amaryllifolius dye mixed with TiO2 was observed at 2:1 of ethanol: water. H.polyrhizus dye extracted by water and mixed with TiO2 demonstrated the highest adsorption among the solvents. All extracted dye was adsorbed onto the surface of TiO2 based on Fourier Transform Infrared Spectroscopy (FTIR) analysis. The inhibition of crystallinity of TiO2 was likewise investigated by X-ray analysis. The morphological properties and composition of dyes were analyzed via SEM and EDX.

The role of physical techniques on the preparation of photoanodes for dye sensitized solar cells

Dye sensitized solar cells (DSSCs) have attracted numerous research, especially in the context of enhancing their efficiency and durability, due to the low-cost and environmentally friendly nature of photovoltaic (PV) technology. The materials in DSSCs are vital towards the realization of these goals, since many of the important components are influenced by their respective preparation and deposition methods. This review aims to detail the research and development aspects of the different physical methods with the purpose of evaluating their prospects and corresponding limitations. The diversity of consideration and criteria includes thin film applications, material characteristics, and process technology that need to be taken into account when selecting a specific deposition method. Choosing a deposition method is not as simple as it seems and is rendered quite complicated due to various factors. Usually, a researcher will evaluate techniques based on factors such as the different preparations and deposition technology with materials’ and substrates’ type, specified applications, costs, and efficiencies.

Electrodeposited p-type Co3O4 with high photoelectrochemical performance in aqueous medium

p-Type Co3O4 photocathodes with different amounts of CuO, were synthesized on fluorine doped tin oxide (FTO) via electrodeposition from a chloride bath containing suspended starch particles. All of the fabricated samples were photoresponsive toward water splitting in 0.5 M Na2SO4 under simulated sun-light. The PEC performance was evaluated using LSPV, chronoamperometry, and EIS techniques. The samples fabricated via the electrodeposition/anodizing/annealing process showed greater photocurrent response compared to the electrodeposition/annealing process. Among all the samples, the sample with an atomic composition% of Co: 24.9, Cu: 25.0 and O: 50.1 showed an optimum photocurrent response (∼6.5 mA cm−2 vs. SCE at −0.3 V). The structure, morphology/composition and optical response were characterized by XRD, FESEM/EDX and UV-Vis techniques, respectively.

Heterojunction Cr2O3/CuO:Ni photocathodes for enhanced photoelectrochemical performance

Heterojunction p-type photoelectrodes consisting of chromium oxide (Cr2O3) and copper oxide (CuO)-doped nickel (Ni) were prepared using aerosol-assisted chemical vapour deposition (AACVD) and spin-coating. All samples were photoresponsive and showed a photocathodic current in 0.5 M Na2SO4 under simulated solar illumination. The photocathode with an optimal composition of 3 layers of CuO and 0.5% Ni showed an enhanced photoactivity relative to bare Cr2O3. Based on the optical characterization and the flatband potential calculation, the fabricated Cr2O3, Cr2O3/CuO and Cr2O3/CuO:Ni can absorb visible light, which enables the water reduction reaction. Moreover, electrochemical impedance spectroscopy revealed that the charge transfer resistance of Cr2O3/CuO:Ni was decreased. Thus, in the heterojunction structure, the photogenerated electrons in Cr2O3 were transferred to the CuO:Ni layer, which then contributes to a high photoactivity. The combined advantages of the two strategies (heterojunction and doping) provide favourable charge transport characteristics of the materials.

An Efficient Metal-Free Hydrophilic Carbon as a Counter Electrode for Dye-Sensitized Solar Cells

This study presents a new cost-effective metal-free counter electrode (CE) for dye-sensitized solar cells (DSSCs). CE was prepared by doctor blading a hydrophilic carbon (HC) particle on a fluorine-doped tin oxide substrate. Thereafter, HC CE was characterized using X-ray diffraction, profilometry, four-point probe testing, and cyclic voltammetry. A 2 µm thick HC CE revealed a comparable catalytic activity to that of the Pt electrode under the same experimental conditions. DSSC based on HC CE was analyzed and showed of 6.87 mA/cm2 close to that of DSSC with Pt CE (7.0 mA/cm2). More importantly, DSSC based on HC CE yielded a power conversion efficiency () of 2.93% under AM 1.5 irradiation (100 mW/cm2), which was comparable to that of DSSC based on standard Pt CE. These findings suggest that HC CE could be a promising CE for low-cost DSSCs.

The architecture of the electron transport layer for a perovskite solar cell

The emergence of perovskite solar cells (PSCs) recently has brought new hope to the solar cell industry due to their incredible improvement of the power conversion efficiency (PCE), which can now exceed 20.0% within seven years of tremendous research. The efficiency and stability of PSCs depend strongly on the morphology and type of materials selected as the electron transport layer (ETL) in the device. In this review, the functions of the ETL based on titania (TiO2) in n–i–p architecture PSCs, including planar heterojunction and mesoporous-structured devices, are reviewed in terms of the device performance and stability. Studies found that the application of suitable fabrication techniques and manipulation of the nanostructural properties of TiO2 are crucial factors in ameliorating the short-circuit current density, JSC, and fill factor, FF, of PSCs. On top of that, the effect of substituting TiO2 with other potential inorganic materials like zinc oxide (ZnO), tin oxide (SnO2), ternary metal oxides, and metal sulphides, as well as organic semiconductors including fullerene, graphene, and ionic liquids, towards the photovoltaic properties and stability of the devices are also elaborated and discussed. Meanwhile, the utilization of non-electron transport layers (non-ETLs), such as alumina (Al2O3) and zirconia (ZrO2), as the mesoporous scaffold in PSCs is found to enhance the open-circuit voltage, VOC, of the devices.

Natural dye extracted from Pandannus amaryllifolius leaves as sensitizer in fabrication of dye-sensitized solar cells

1 Department of Chemical and Process Engineering, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor, Malaysia 2 Solar Energy Research Institute (SERI), Universiti Kebangsaan Malaysia, Bangi, 43600 Selangor, Malaysia 3 Fuel Cell Institute, Universiti Kebangsaan Malaysia, Bangi, 43600 Selangor, Malaysia 4 Department of Biology, College of Education for Pure Sciences/Ibn Al-Haitham, University of Baghdad, Baghdad, Iraq * Email address: mamash73@yahoo.com

Progress towards highly stable and lead-free perovskite solar cells

High-performance perovskite solar cells have attracted increased attention for photovoltaic applications and potentially replacing the predecessor generations. Nevertheless, the stability issues and the lead content has always been among the major concerns that barriers perovskite solar cells from commercialization. This review presents the discussion towards the inherent instability of perovskite solar cells and the development towards replacing lead with discussion towards their performance and challenges. The degradation of perovskite active layer would release toxic substance into the environment. The development towards low-toxic, lead-free and efficient perovskite solar cells is the key for a sustainable solar energy generation with the application of perovskite solar cells.